For large cluster , there will be a lot of change at any time, this means the pressure of mon will be big at some time, because all change will go through leader , so for this , the local storage for mon should be good enough, I think this maybe a conderation . On Tue, Jul 11, 2017 at 11:29 AM, Brad Hubbard <bhubbard@xxxxxxxxxx> wrote: > On Tue, Jul 11, 2017 at 3:44 AM, David Turner <drakonstein@xxxxxxxxx> wrote: >> Mons are a paxos quorum and as such want to be in odd numbers. 5 is >> generally what people go with. I think I've heard of a few people use 7 >> mons, but you do not want to have an even number of mons or an ever growing > > Unless your cluster is very large three should be sufficient. > >> number of mons. The reason you do not want mons running on the same >> hardware as osds is resource contention during recovery. As long as the Xen >> servers you are putting the mons on are not going to cause any source of >> resource limitation/contention, then virtualizing them should be fine for >> you. Make sure that you aren't configuring the mon to run using an RBD for >> its storage, that would be very bad. >> >> The mon Quorum elects a leader and that leader will be in charge of the >> quorum. Having local mons doesn't do anything as the clients will still be >> talking to the mons as a quorum and won't necessarily talk to the mon >> running on them. The vast majority of communication to the cluster that >> your Xen servers will be doing is to the OSDs anyway, very little >> communication to the mons. >> >> On Mon, Jul 10, 2017 at 1:21 PM Massimiliano Cuttini <max@xxxxxxxxxxxxx> >> wrote: >>> >>> Hi everybody, >>> >>> i would like to separate MON from OSD as reccomended. >>> In order to do so without new hardware I'm planning to create all the >>> monitor as a Virtual Machine on top of my hypervisors (Xen). >>> I'm testing a pool of 8 nodes of Xen. >>> >>> I'm thinking about create 8 monitor and pin one monitor for one Xen node. >>> So, i'm guessing, every Ceph monitor'll be local for each node client. >>> This should speed up the system by local connecting monitors with a >>> little overflown for the monitors sync between nodes. >>> >>> Is it a good idea have a local monitor virtualized on top of each >>> hypervisor node? >>> Did you see any understimation or wrong design in this? >>> >>> Thanks for every helpfull info. >>> >>> >>> Regards, >>> Max >>> >>> _______________________________________________ >>> ceph-users mailing list >>> ceph-users@xxxxxxxxxxxxxx >>> http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com >> >> >> _______________________________________________ >> ceph-users mailing list >> ceph-users@xxxxxxxxxxxxxx >> http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com >> > > > > -- > Cheers, > Brad > _______________________________________________ > ceph-users mailing list > ceph-users@xxxxxxxxxxxxxx > http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com _______________________________________________ ceph-users mailing list ceph-users@xxxxxxxxxxxxxx http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
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